I've got a newer 440 MP distributor that I cannot adjust the vacuum advance enough to get it to stop spark-knocking. I also have an old unadjustable electronic unit that works way better. What's going on here?

maybe u just have too much total. the adj vac thing is misleading. you can't adj how much. u can only adj. how much vac it takes to pull it in. they are pre set. take the # on the the arm and double it thats how much it pulls in when it sees the vac. u adj. it for. some say epoxy a piece of metal on the arm to stop it for the amount you want pulled in.

Dcuda69, 50-52 degrees is just about where you want to be when you add up all the numbers. The engine will very seldom be at 50.

The small block MP distributor i just set-up a couple of weeks ago had a vacuum pod that would add 17 degrees of timing at full stroke and was adjusted so it started coming in at 9" Hg and was all in at 18" Hg.

paironines, does it knock if you have the vacuum advance disconnected?

Also, you turn the adjustement screw counter clockwise to to move the vacuum required to stroke the pod up and clockwise to move it down.

What is you initial timing set at, what the total mechanical and what rpm is it all in at?

Dave,

The newer Mopar Dist have a very fast advance curve out of the box, some of them have very light springs and bounce in and out of advance, I would check this along with Innitial and total timing...........Paul

Out of the box, mine had 28° of mechanical advance that came in by about 3000, and terrible spark scatter. The newer ones have an adjustable plate under the reluctor. There are 2 T-15 Torx screws that you loosen to slide the tabs in the slots open or closed to add or decrease total mechanical advance. I closed mine about 1/2 way and now have 14° of travel. It also causes it to come in earlier. I run 21° initial with 35° by 2800 on my 496" stroker. The spark scatter was hepled greatly by siding a length of 1/2" rubber fuel line over the shaft, cut a long enough that it compresses about 1/8" against the oil pump drive gear when the distributor is tightened down. It acts as a dampener.

I do not run the vacuum advance.

Mine does the same thing its because it advances the timing too fast it does it if the vacum hose is hooked up or not. You can buy a kit with a bunch of different springs and plastic keys to adjust it all properly. Or you can set the timing back and it will stop it too.

The two sb MP distributors I have had both had 24 degrees of advance in the plate but one had two pink (lightest) springs and the other had one brown (the next one up from pink) and a two stage sping with the oblong loop.

The one I mentioned above was adjusted to 16 degrees of mechanical with tow brown springs. This has the advance all in at 2600 rpm and combined with the 17 intial gives me 33 total mechanical.

With the 17 in the vacuum pod I can have as much as 50 degrees at light throttle cruise.